Verification of Architectural Refactorings: Rule Extraction and Tool Support

Software in use needs to be adapted to changing requirements, otherwise it becomes obsolete. Often, this involves changing the architecture of the system. To avoid the introduction of unwanted or removal of desired behaviour, these changes need verification. While verifying large systems consumes considerable resources, the verification of only the changed parts can, under certain conditions, give the required assurance. This opens the possibility of creating formally verified, reusable refactoring patterns. However, a mechanism for extracting such patterns is needed. To address this problem, a theoretical framework is presented that allow to formally reason about the rule extraction process. In order to harness the theoretical results, a visual editor and tool chain are introduced to aid developers in extracting refactoring rules and prove their behavioural correctness

Evolving Software Systems for Self-Adaptation

There is a strong synergy between the concepts of evolution and adaptation in software engineering: software adaptation refers to both the current software being adapted and to the evolution process that leads to the new adapted software. Evolution changes for the purpose of adaptation are usually made at development or compile time, and are meant to handle predictable situations in the form of software change requests. On the other hand, software may also change and adapt itself based on the changes in its environment. Such adaptive changes are usually dynamic, and are suitable for dealing with unpredictable or temporary changes in the software's operating environment. A promising solution for software adaptation is to develop self-adaptive software systems that can manage changes dynamically at runtime in a rapid and reliable way. One of the main advantages of self-adaptive software is its ability to manage the complexity that stems from highly dynamic and nondeterministic operating environments. If a self-adaptive software system has been engineered and used properly, it can greatly improve the cost-effectiveness of software change through its lifespan. However, in practice, many of the existing approaches towards self-adaptive software are rather expensive and may increase the overall system complexity, as well as subsequent future maintenance costs. This means that in many cases, self-adaptive software is not a good solution, because its development and maintenance costs are not paid off. The situation is even worse in the case of making current (legacy) systems adaptive. There are several factors that have an impact on the cost-effectiveness and usability of self-adaptive software; however the main objective of this thesis is to make a software system adaptive in a cost-effective way, while keeping the target adaptive software generic, usable, and evolvable, so as to support future changes. In order to effectively engineer and use self-adaptive software systems, in this thesis we propose a new conceptual model for identifying and specifying problem spaces in the context of self-adaptive software systems. Based on the foundations of this conceptual model, we propose a model-centric approach for engineering self-adaptive software by designing a generic adaptation framework and a supporting evolution process. This approach is particularly tailored to facilitate and simplify the process of evolving and adapting current (legacy) software towards runtime adaptivity. The conducted case studies reveal the applicability and effectiveness of this approach in bringing self-adaptive behaviour into non-adaptive applications that essentially demand adaptive behaviour to sustain

Erlang programok statikus elemzése és szeletelése

A funkcionális programozási nyelvek terjedésének velejárója, hogy felmerül az igény olyan eszközökre, amelyek a fejlesztési folyamatot támogatják. Ezek lehetnek futási idejű eszközök, vagy olyanok, melyek csupán a forráskód elemzésével kı́nálnak hasznos információkat a fejlesztők számára. Az Erlang ipari környezetben is gyakran használt funkcionális programozási nyelv. A RefactorErl egy statikus elemző és refaktoráló eszköz Erlanghoz, mely számos transzformációt biztosı́t a forráskód jelentésmegőrző átalakı́tására, másrészről kiterjedt statikus elemzőkészlettel segı́ti a fejlesztőket a mindennapos tevékenységükben. Kutatásomban olyan elemzési módszerekkel foglalkoztam, amelyek segı́tségével az Erlang programok forráskódjában rejlő összetett összefüggések nyerhetők ki. Ezek az eredmények pedig további magasabb szintű elemzések alapját képzik. Az ismertetett eredményeim a vezérlés és az Erlang folyamatok közötti kapcsolatok elemzéséhez kapcsolódnak. A dolgozatomban Erlang programok vezérlésfolyam-gráfját adtam meg, amely tartalmazza a programok végrehajtása során előálló lehetséges végrehajtási utakat. A gráfot a nyelv szintaktikus kategóriáihoz rendelt formális szabályok segı́tségével definiáltam, amelyek a nyelv szemantikájának megfelelően adják meg a vezérlésfolyam-gráf éleit. A vezérlésfolyam-gráf felhasználásra került további elemzésekhez is, mint például a párhuzamosı́tható komponensek azonosı́tása. A vezérlésfolyam-gráf, illetve a benne foglalt információk felhasználhatóak a forráskódban történő változások hatáselemzéséhez. A vezérlésfüggőségi gráf egy kompaktabb reprezentáció, amely a vezérlési utakban lévő szekvenciák eliminálásával már csak a kifejezések közötti közvetlen függőségeket tartalmazza. Megadtam Erlang programokra a vezérlésfüggőségi gráfot, amelyet adatfüggőségi információkkal egészı́tettem ki. Az ı́gy definiált Erlang függőségi gráf felhasználható gráf alapú statikus programszeleteléshez. A definiált infrastruktúrára épı́tve megadtam egy hatáselemzés alapú teszteset szelekciós módszert. A módszer azon tesztesetek halmazát adja meg, amelyek érintettek lehetnek a változtatás/transzformáció kapcsán. Azaz a változtatás hatása elterjedhet a tesztelt funkcionalitásba. Az elemzés nem csak a transzformációk hatásának elemzésére, hanem tetszőleges változás elemzésére is használható. Dolgozatomban bemutattam Erlang programok egy statikus kommunikációs modelljét. Megadtam azokat az algoritmusokat, melyek segı́tségével felderı́thetőek az elindı́tott Erlang folyamatok és a köztük aszinkron üzenetküldésekkel lebonyolı́tott kommunikáció. A modellbe felvettem olyan rejtett kommunikációs elemeket is, mint a közös osztott memóriának tekinthető Erlang Term Storage (ets) táblák használata. Megadtam azokat a statikus elemzési algoritmusokat, melyek felhasználásával kiegészı́thető a kommunikációs gráf speciális Erlang folyamatokkal (például generikus szerverek) és az interfészeiken keresztül történő rejtett kommunikációval. A kommunikációs gráf kiválóan használható a kódban rejlő összefüggések megjelenı́tésére, kódmegértés, konkurenciából fakadó hibakeresés támogatásához. Ugyanakkor felhasználható konkurens programok változásához köthető hatáselemzés pontosı́tásához is

An Algebra of Hierarchical Graphs

We define an algebraic theory of hierarchical graphs, whose axioms characterise graph isomorphism: two terms are equated exactly when they represent the same graph. Our algebra can be understood as a high-level language for describing graphs with a node-sharing, embedding structure, and it is then well suited for defining graphical representations of software models where nesting and linking are key aspects

I Can See Clearly Now: Clairvoyant Assertions for Deadlock Checking

Under embargo until: 2023-07-04Static analysers are traditionally used to check various correctness properties of software. In the face of refactorings that can have adverse effects on correctness, developers need to analyse the code after refactoring and possibly revert their changes. Here, we take a different approach: we capture the effect of the Hide Delegate refactoring on programs in the ABS modelling language in terms of the base program, which allows us to predict the correctness of the refactored program. In particular, we focus on deadlock-detection. The actual check is encoded with the help of an additional data structure and assertions. Developers can then attempt to discharge assertions as vacuous with the help of a theorem prover such as KeY. On the one hand, this means that we do not require a specific static analyser nor theorem prover, but rather profit from the strength and advances of modern tool support. On the other hand, developers can choose to rely on existing tests to confirm that no assertion is triggered before executing the actual refactoring. Finally, we argue the correctness of our over-approximation.acceptedVersio

Fundamental Approaches to Software Engineering

computer software maintenance; computer software selection and evaluation; formal logic; formal methods; formal specification; programming languages; semantics; software engineering; specifications; verificatio

Remedy of Mixed Initiative Conflicts in Model-based System Engineering

SPACE is a technique for model-driven engineering of reactive distributedsystems. One of the strengths of its tool-set Arctis is that the system engineercan formally analyze the models for design errors such that these can becorrected early in the development process. In this paper, we go a step further andintroduce a technique that refines the fault detection and, in addition, offers a highlyautomatic mechanism to remedy the errors. For that, we combine model checking,the already existing analysis method of Arctis, with graph transformation. Usinggraph rewriting rules, we can analyze the state space graph of a system for the exact reason of an error as well as remove the erroneous parts of a model by changing themodel description. We exemplify the approach by envisaging the detection and remedyof mixed initiatives, a quite common cause for faulty behavior in event-drivensystems that often is overlooked in system development

Quality Assurance of Software Models - A Structured Quality Assurance Process Supported by a Flexible Tool Environment in the Eclipse Modeling Project

The paradigm of model-based software development (MBSD) has become more and more popular since it promises an increase in the efficiency and quality of software development. In this paradigm, software models play an increasingly important role and software quality and quality assurance consequently leads back to the quality and quality assurance of the involved models. The fundamental aim of this thesis is the definition of a structured syntax-oriented process for quality assurance of software models that can be adapted to project-specific and domain-specific needs. It is structured into two sub-processes: a process for the specification of project-specific model quality assurance techniques, and a process for applying them on concrete software models within a MBSD project. The approach concentrates on quality aspects to be checked on the abstract model syntax and is based on quality assurance techniques model metrics, smells, and refactorings well-known from literature. So far, these techniques are mostly considered in isolation only and therefore the proposed process integrates them in order to perform model quality assurance more systematically. Three example cases performing the process serve as proof-of-concept implementations and show its applicability, its flexibility, and hence its usefulness. Related to several issues concerning model quality assurance minor contributions of this thesis are (1) the definition of a quality model for model quality that consists of high-level quality attributes and low-level characteristics, (2) overviews on metrics, smells, and refactorings for UML class models including structured descriptions of each technique, and (3) an approach for composite model refactoring that concentrates on the specification of refactoring composition. Since manually reviewing models is time consuming and error prone, several tasks of the proposed process should consequently be automated. As a further main contribution, this thesis presents a flexible tool environment for model quality assurance which is based on the Eclipse Modeling Framework (EMF), a common open source technology in model-based software development. The tool set is part of the Eclipse Modeling Project (EMP) and belongs to the Eclipse incubation project EMF Refactor which is available under the Eclipse public license (EPL). The EMF Refactor framework supports both the model designer and the model reviewer by obtaining metrics reports, by checking for potential model deficiencies (called model smells) and by systematically restructuring models using refactorings. The functionality of EMF Refactor is integrated into standard tree-based EMF instance editors, graphical GMF-based editors as used by Papyrus UML, and textual editors provided by Xtext. Several experiments and studies show the suitability of the tools for supporting the techniques of the structured syntax-oriented model quality assurance process

SAVCBS 2004 Specification and Verification of Component-Based Systems: Workshop Proceedings

This is the proceedings of the 2004 SAVCBS workshop. The workshop is concerned with how formal (i.e., mathematical) techniques can be or should be used to establish a suitable foundation for the specification and verification of component-based systems. Component-based systems are a growing concern for the software engineering community. Specification and reasoning techniques are urgently needed to permit composition of systems from components. Component-based specification and verification is also vital for scaling advanced verification techniques such as extended static analysis and model checking to the size of real systems. The workshop considers formalization of both functional and non-functional behavior, such as performance or reliability